In Larix settings (the ⚙️ icon), go to "Connections" and create a new Connection with the following details:
Name: Bandcamp
Target type: Default (no authorization)
URL: rtmp://global-live.mux.com:5222/app/STREAM_KEY_GOES_HERE
Mode: Audio + Video
Back in the settings page, go to Capture and encoding and input the following settings within the "Video" section under Broadcasting:
Resolution: 1280x720
Orientation: Landscape
Multi-camera capture: Off
Stabilization mode: Off
Live rotation: Off